The overall objective of the proposed studies is to continue microbiological and biochemical analysis of unique characteristics which allow specific bacteria to survive in the human oral cavity, interact and become a part of dental plaque, and initiate dental caries on the tooth surface. The specific objectives of these studies are: 1. To utilize purified and characterized glucosyltransferases from Streptococcus mutans to determine the mechanism of water-insoluble adherent glucan production by this bacterium. 2. To determine the role in glucan production from sucrose of the endohydrolytic dextranase produced by S. mutans. 3. To continue evaluation of the role of indigenous dextranase-producing oral bacteria in regulating the retention in the mouth and cariogenicity of glucan-producing oral streptococci and lactobacilli. 4. To analyze structure of the bacterial and host factors involved in isotypic and heterotypic oral bacterial cell-cell interactions and oral bacterial cell-solid surface adherence reactions.